/*
 *  Copyright (c) WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
 *
 *  WSO2 Inc. licenses this file to you under the Apache License,
 *  Version 2.0 (the "License"); you may not use this file except
 *  in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.wso2.balana.xacml2;

import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.wso2.balana.*;
import org.wso2.balana.attr.AttributeFactory;
import org.wso2.balana.attr.AttributeValue;
import org.wso2.balana.ctx.Attribute;
import org.wso2.balana.ctx.EvaluationCtx;
import org.wso2.balana.ctx.xacml2.Result;

import java.io.OutputStream;
import java.io.PrintStream;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * Represents ObligationType in the XACML 2.0 policy schema. In XACML 2.0, this
 * element represent both in policy and result. Therefore this has extends the
 * <code>AbstractObligation</code> and implements the
 * <code>ObligationResult</code>
 */
public class Obligation extends AbstractObligation implements ObligationResult {

	/**
	 * A <code>List</code> of <code>Attribute</code>
	 */
	private List<Attribute> assignments;

	/**
	 * Constructor that takes all the data associated with an obligation. The
	 * attribute assignment list contains <code>Attribute</code> objects, but
	 * only the fields used by the AttributeAssignmentType are used.
	 * 
	 * @param obligationId
	 *            the obligation's id
	 * @param fulfillOn
	 *            the effect denoting when to fulfill this obligation
	 * @param assignments
	 *            a <code>List</code> of <code>Attribute</code>s
	 */
	public Obligation(URI obligationId, int fulfillOn,
			List<Attribute> assignments) {
		this.obligationId = obligationId;
		this.fulfillOn = fulfillOn;
		this.assignments = Collections
				.unmodifiableList(new ArrayList<Attribute>(assignments));
	}

	/**
	 * Creates an instance of <code>Obligation</code> based on the DOM root
	 * node.
	 * 
	 * @param root
	 *            the DOM root of the ObligationType XML type
	 * 
	 * @return an instance of an obligation
	 * 
	 * @throws ParsingException
	 *             if the structure isn't valid
	 */
	public static Obligation getInstance(Node root) throws ParsingException {

		URI id;
		int fulfillOn;
		String effect;
		List<Attribute> assignments = new ArrayList<Attribute>();

		AttributeFactory attrFactory = Balana.getInstance()
				.getAttributeFactory();
		NamedNodeMap attrs = root.getAttributes();

		try {
			id = new URI(attrs.getNamedItem("ObligationId").getNodeValue());
		} catch (Exception e) {
			throw new ParsingException(
					"Error parsing required attribute ObligationId", e);
		}

		try {
			effect = attrs.getNamedItem("FulfillOn").getNodeValue();
		} catch (Exception e) {
			throw new ParsingException(
					"Error parsing required attribute FulfillOn", e);
		}

		if (effect.equals("Permit")) {
			fulfillOn = Result.DECISION_PERMIT;
		} else if (effect.equals("Deny")) {
			fulfillOn = Result.DECISION_DENY;
		} else {
			throw new ParsingException("Invalid Effect type: " + effect);
		}

		NodeList nodes = root.getChildNodes();
		for (int i = 0; i < nodes.getLength(); i++) {
			Node node = nodes.item(i);
			if (node.getNodeName().equals("AttributeAssignment")) {
				try {
					URI attrId = new URI(node.getAttributes()
							.getNamedItem("AttributeId").getNodeValue());
					AttributeValue attrValue = attrFactory.createValue(node);
					assignments.add(new Attribute(attrId, null, null,
							attrValue, XACMLConstants.XACML_VERSION_2_0));
				} catch (URISyntaxException use) {
					throw new ParsingException("Error parsing URI", use);
				} catch (UnknownIdentifierException uie) {
					throw new ParsingException(uie.getMessage(), uie);
				} catch (Exception e) {
					throw new ParsingException(
							"Error parsing attribute assignments", e);
				}
			}
		}

		return new Obligation(id, fulfillOn, assignments);
	}

	@Override
	public ObligationResult evaluate(EvaluationCtx ctx) {
		return new Obligation(obligationId, fulfillOn, assignments);
	}

	/**
	 * Returns the id of this obligation
	 * 
	 * @return the id
	 */
	public URI getId() {
		return obligationId;
	}

	/**
	 * Returns the attribute assignment data in this obligation. The
	 * <code>List</code> contains objects of type <code>Attribute</code> with
	 * only the correct attribute fields being used.
	 * 
	 * @return the assignments
	 */
	public List<Attribute> getAssignments() {
		return assignments;
	}

	/**
	 * Encodes this <code>Obligation</code> into its XML form and writes this
	 * out to the provided <code>OutputStream<code> with no indentation.
	 * 
	 * @param output
	 *            a stream into which the XML-encoded data is written
	 */
	public void encode(OutputStream output) {
		encode(output, new Indenter(0));
	}

	/**
	 * Encodes this <code>Obligation</code> into its XML form and writes this
	 * out to the provided <code>OutputStream<code> with indentation.
	 * 
	 * @param output
	 *            a stream into which the XML-encoded data is written
	 * @param indenter
	 *            an object that creates indentation strings
	 */
	public void encode(OutputStream output, Indenter indenter) {

		PrintStream out = new PrintStream(output);
		String indent = indenter.makeString();

		out.println(indent + "<Obligation ObligationId=\""
				+ obligationId.toString() + "\" FulfillOn=\""
				+ Result.DECISIONS[fulfillOn] + "\">");

		indenter.in();

		for (Attribute assignment : assignments) {
			out.println(indenter.makeString()
					+ "<AttributeAssignment AttributeId=\""
					+ assignment.getId().toString() + "\" DataType=\""
					+ assignment.getType().toString() + "\">"
					+ assignment.getValue().encode() + "</AttributeAssignment>");
		}

		indenter.out();

		out.println(indent + "</Obligation>");
	}
}
